Electrical heating and cooking apparatus



C. G. AND W. W. NOBBS.

ELECTRICAL HEATING AND COOKING APPARATUS.

APPLICATION FILED DEC.26, 1918.

Patented June 29, 1920.

UNiTEe sT-ATES g PATENT OFFICE;

CORNELIUS GEORGE IN'OBBS AND WALTER `ILLIAM NOBBS, OF LONIJON, '.EIBTGLAN'D.V

ELECTRICAL HEATING AND oooKING APPARATUS.

` Application filed Deember 26, 1918. seriai No. 268,310.

which heating conductors 4in the form 'of wires or. strips were wound on flat strips or mica orother suitable insulating lsupports and when externally :covered by similarly `shaped strips of mica or'the likerwcrev in-V serted'in an outer protecting vcoverof copperv vor other suitable material, preferably, of

elliptical cross section. After `the insertion of the heating coil the cover was compressed into a llat tubular 'form with rounded edges and incurved sides in .order to insure intimate heat conducting'contact between vthe inclosed parts andtheouter cover. y f "The current was led to a central conductor in the Vform of a stripA of the samewidth as'the insulating Asupports between rwhich lit was inclosed andreturned a wirejor strip wound on the flat insulatingstrips. y In one form oil the invention the central *con-l ducto'r was connected to twojwires wound separately on insulating strips and inclosed in the ysame protecting cover.

According to the present invention, which consists in modifications or improvements of the constructions described in the prior i specilication, the mica or other insulation,

placed between the conducting wires or strips and the `metal cover, is protected against damage, which is liable to occur during the process of compressingthe outer envelop and inserting or removing the heating element, by the interposition of a metal sheath between the insulation and the cover. The ends of the protecting envelop are, preferably, reduced in longitudinal section to a form which tends to prevent the formation of eddy currents and lessens the resistanceto the circulation of the fluid in which the heating device is immersed.` The block to which the leading in terminals are secured is placed at the top or bot- Specification of Letters Patent. l Patented ,Ill-119,

'li uid to be heated; y

y tom side instead of at the end yof the heater,

a`lso,*in order to facilitate theV flow of fluid pastthe heater.

In the accompanying `drawings which represent an example of a construction according to the invention, Figure l is a sectional elevation of the heater immersed in the lig. 2 is a section on the line 2-2. of Fig. l; l 'f p Fig is `an elevation on'a larger scale of the heater, with part of the cover removed; F ig. 4 is a plan view as seenfr'rom below and Fig.. 5 isa cross section of the heater.

The heating element lcomprises a wire 4or l strip 1, preferably, ofnickel chromium (nichrome) wound around insulating supports 2 and 3 of mica. In the example shown the conductor l isk connected with lone ofthe l leading in terminals 4 and 5 and after being `wound vspirally around one of the insulating supports 2 or 3 to the end of 'the heating elem/ent returns by a similar spiral winding around the kother insulating vsupport to the other terminal. A centralstrip 6 of micajinsulates the adjacent windingslof. the conductor. Strips "7 and 8 of mica insulate the conductor from a cover 9 and from a kmetal sheath 1'0, which is inserted between the mica insulation 7 andS and the cover; in order, as explainedabovc, toy prevent any ldamage occurring tothe `mica insulation during itsV insertion in or removal from the cover 9i or thevprocess of compressing kthe Qfcross sectionvof the'cover from a vcircular or elliptic orm'into a 'flattened and slightly incurved section with rounded edges as shown in Fig. 5, the sheath 10 is of tubular `form as shown by the dotted lines in Fig. 4f,

the resistor being inserted through the open ends of the tube before the latter is placed within the cover 9. As described in the prior specification this form maintains all the parts of the heating element in intimate contact and insures good thermal conductivity with the outer envelop.

The invention is lnot limited tothe arrangement in which the conductor is wound around two insulating supports in series as shown in Fig. 5; other arrangements of the conducting wire may be employed, such as ythe single insulating support shown in the prior specification referred to. Also, al-

l face of the vessel.

though mica has been described as the insulating medium other suitable material may be employed for the purpose.

The ends 11 and 12 of the cover 9, beyond the limits of the conducting wire and its supports, arereduced in section to the form shown in order to facilitate the flow of the circulating liquid in the vessel or conduit in which the heating element is immersed.

The connection with the leading in terminals is made at the lower side of the element as shown in Figs. 1, 3 and 4. In the example illustrated a saddle shaped member 13, conforming to the internal surface of the vessel or conduit 15 in which the heating element is to be immersed, is soldered to the cover 9; a rubber seating 14 being interposed between the member 13 and the sur- A block 16 of ebonite or other insulating material is secured to the member 13 by screws 17. The leading in wires 18 of the heating conductor 1 are brought into the hollow bases of the terminal sockets 4 and 5 and are secured by set screws 19 and 20.

The arrangement according to the invention is adapted generally forluse in electric heating and cooking apparatus and is also especially applicable for warming the water for Aradiators for internal combustion engines in cases where such water is liable to freeze, as when the engines have been shut down and the radiators are exposed to very low temperatures. Such conditions are especially likely to occur, as is well known, in the working of aeroplane engines.

Having thus described the nature of the said invention and the best means we know of carrying the same into practical effect, we claim 1. An electric heating device of the immersion type comprising in combination a flat strip of insulating material, a conductor wound thereon, insulating strips in contact with either surface of said conductor, a metal sheath open at the longitudinal sides extending above and below over the whole breadth of the conductor and a protecting cover inclosing the whole and pressed into intimate contact with said sheath, the said protecting cover being in direct contact with the liquid to be heated.

2. An electric heating device of the immersion type comprising in combination a Hat strip of insulating material, a conductor Y wound thereon, insulating strips in contact with either surface of said conductor, a metal sheath open at the longitudinal sides extending above and below over the whole breadth of the conductor and a protecting cover with rounded edges and incurved sides inclosing the whole and pressed into intimate contact with said sheath.

3. An electric heating device of the immersion ,type comprising in combination a flat strip of insulating material, a conductor wound thereon, insulating strips in contact with either surface of said conductor, a metal sheath protecting said conductor and said insulating strips, a protecting cover, a saddle shaped member embracing said cover and conforming to the shape of the vessel in which the heating device is immersed, an insulating seating between said member and the vessel, an insulating block secured b v screws to said member, and hollow terminal sockets on said block in which sockets the ends of the conductor are secured.

4. An electric heating device of the immersion type comprising in combination a flat strip of insulating material, a fcondue tor wound thereon, a second flat strip of insulating material on which a continuation of the said conductor is wound, a strip of insulating material placed between the strips on which the conductor is wound and strips of insulating material on either side of the conductor, an outer protecting cover and a metal sheath between said cover and the insulating strips provided on either side of the conductor,

In testimony whereof we have signed our names to this specification.

CORNELIUS GEORGE NOBBS. WALTER VILLIAM NOBBS. 

